We plan to study the structure and function of ribosomal RNA and ribosomes, as well as related RNA such as messenger and transfer RNA. We shall continue to concentrate on comparative studies involving mitochondrial and cytoplasmic protein-synthesizing systems, and the mRNA that programs these systems, in normally growing animal cells, in cells infected by the alphavirus Sindbisand the flavivirus Dengue, and in a variety of prokaryotic cells. Samples labeled with radioactive methionine, phosphate and/or uridine will be obtained and will be subjected to general sequence analysis, and also to analysis of minor (especially methylated) nucleotides, and of 5'-termini in particular. Methodology will include alkaline, acid, and enzymatic digestion; paper electrophoresis and chromatography; DEAE cellulose column chromatography; two-dimensional oligonucleotide finger-printing; and terminal labeling followed by multiple partial endonuclease digestion and "ladder" type sequence analysis.